Many attempts have ben made to supplant the dominance of plain wire paper clips with paper clips of improved performance. Generally the improvements have been to the shape or surface texture of wire clips or have involved the use of different materials, such as plastic, in part for the purpose of increasing the gripping surface. Plain wire paper clips have known deficiencies. While they are typically coated with a rust retardant material, they are still subject to rusting under high humidity conditions. In addition, the gripping force of the conventional clip is limited by several inherent factors including the fact that the plain wire paper clip with its rounded cross-sectional configuration has a very small area of contact with the paper surface. In addition, the considerations of ease of paper insertion, and minimization of paper damage, limits the spring force which can be built into such a conventional clip.
U.S. Pat. No. 3,913,181 represents an attempt to improve the performance of conventional clips by applying a coating to a paper gripping surface. The coating generally conforms to the exterior configuration of the wire and therefore cannot reduce the tendency of the clip to pick up unintended additional papers. Also the paper contact area is not significantly increased, again because of the conformity of the coating to the paper clip surface.
In U.S. Pat. No. 4,055,874, the contact area is increased dramatically but at the expense of considerable additional material and manufacturing complexity. There is no attempt to reduce the likelihood of picking up extra papers.
No prior art paper clip shows recognition of or provides structure to deal successfully with the problem of inadvertently picking up extra papers. The misfiling and other loss that such inadvertently attached papers can cause is of potentially calamitous significance.
It is therefore desirable to have a paper clip with improved gripping performance which at the same time, by its design, reduces the likelihood of extra papers being inadvertently picked up by the clip. Such a clip is particularly desirable where it does not corrode.